A 21-year-old woman told cops she was raped by a stranger who got into her Brooklyn apartment and then covered her mouth with a cloth containing a substance that made her pass out, police and sources said Tuesday.

The man – who was wearing a ski mask and gloves – entered the young woman’s flat in Cypress Hills and grabbed her around 4:30 p.m. Monday, police said.

The woman told cops she lost consciousness after he put a cloth over her mouth. When she awoke, she was tied up in her bra and underwear and in pain, the sources said.

Her 9-month-old son was in the apartment but wasn’t harmed.

She was taken to Kings County Hospital, where a rape kit was performed. Cops said it wasn’t clear how the man, a stranger, got into the home.

Police said there was no description available and an investigation was being conducted by the Brooklyn Special Victims Squad.